//检查图片的格式是否正确,同时实现预览
function onUploadImgChange(fileObj, imgPreviewId, divPreviewId)
{
	if( !fileObj.value.match(/.jpg|.gif|.png|.bmp|.swf/i)){
	  alert('图片格式无效！');
	  return false;
	}
	
    var browserVersion = window.navigator.userAgent.toUpperCase();
    
    if (fileObj.files) {//兼容chrome、火狐7+、360浏览器5.5+等，应该也兼容ie10，HTML5实现预览
        if (window.FileReader) {
            var reader = new FileReader();
            reader.onload = function(e) {
                document.getElementById(imgPreviewId).setAttribute("src", e.target.result);
            }
            reader.readAsDataURL(fileObj.files[0]);
        } else if (browserVersion.indexOf("SAFARI") > -1) {
            alert("不支持Safari浏览器6.0以下版本的图片预览!");
        } else {
            alert("不支持您当前使用的浏览器的图片预览!");
        }
    } else if (browserVersion.indexOf("MSIE") > -1) {//ie、360低版本预览
        if (browserVersion.indexOf("MSIE 6") > -1) {//ie6
            document.getElementById(imgPreviewId).setAttribute("src", fileObj.value);
        } else {//ie[7-9]
            fileObj.select();
            if (browserVersion.indexOf("MSIE 9") > -1) {
                //fileObj.blur(); //不加上document.selection.createRange().text在ie9会拒绝访问
                document.getElementById(divPreviewId).focus(); //参考http://gallop-liu.iteye.com/blog/1344778
            }
            var newPreview = document.getElementById(divPreviewId + "New");
            if (newPreview == null) {
                newPreview = document.createElement("div");
                newPreview.setAttribute("id", divPreviewId + "New");
                newPreview.style.width = document.getElementById(imgPreviewId).width + "px";
                newPreview.style.height = document.getElementById(imgPreviewId).height + "px";
                newPreview.style.border = "solid 1px #d2e2e2";
            }
            newPreview.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod='scale',src='" + document.selection.createRange().text + "')";
            var tempDivPreview = document.getElementById(divPreviewId);
            tempDivPreview.parentNode.insertBefore(newPreview, tempDivPreview);
            tempDivPreview.style.display = "none";
        }
    } else if (browserVersion.indexOf("FIREFOX") > -1) {//firefox
        var firefoxVersion = parseFloat(browserVersion.toLowerCase().match(/firefox\/([\d.]+)/)[1]);
        if (firefoxVersion < 7) {//firefox7以下版本
            document.getElementById(imgPreviewId).setAttribute("src", fileObj.files[0].getAsDataURL());
        } else {//firefox7.0+                    
            document.getElementById(imgPreviewId).setAttribute("src", window.URL.createObjectURL(fileObj.files[0]));
        }
    } else {
        alert("不支持您当前使用的浏览器的图片预览!");
    }
}
/*
function onUploadImgChange(sender,id){
	if( !sender.value.match(/.jpg|.gif|.png|.bmp|.swf/i)){
	  alert('图片格式无效！');
	  return false;
	}
	
	var objPreview = document.getElementById(id);
	var objPreviewFake = document.getElementById(id+'_fake' );
	if( sender.files &&sender.files[0] ){
	  objPreview.style.display ='block';
	  objPreview.style.width ='auto';
	  objPreview.style.height ='auto';
	  // Firefox 因安全性问题已无法直接通过input[file].value
	  objPreview.src =sender.files[0].getAsDataURL();
	}else if( objPreviewFake.filters){
	  // IE7,IE8 在设置本地图片地址为 img.src 时出现莫名其妙的后果
	  //（相同环境有时能显示，有时不显示），因此只能用滤镜来解决
	 
	  // IE7, IE8因安全性问题已无法直接通过 input[file].value 获取完整的文件路径
	  sender.select();
	  var imgSrc =document.selection.createRange().text;  
	  objPreviewFake.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src= imgSrc;
	  autoSizePreview( objPreviewFake,300,300 );
	  objPreview.style.display ='none';
	}
	
}

function onPreviewLoad(sender){
	autoSizePreview(sender,sender.offsetWidth, sender.offsetHeight );
}

function autoSizePreview( objPre, originalWidth, originalHeight){
	var zoomParam = clacImgZoomParam( 260, 260, originalWidth,originalHeight);
	objPre.style.width = zoomParam.width +'px';
	objPre.style.height = zoomParam.height +'px';
	objPre.style.marginTop = zoomParam.top +'px';
	objPre.style.marginLeft = zoomParam.left + 'px';
}

function clacImgZoomParam( maxWidth, maxHeight, width, height ){
	var param = { width:width, height:height, top:0, left:0 };
	if(width>maxWidth || height>maxHeight ){
	  rateWidth = width /maxWidth;
	  rateHeight = height /maxHeight;  
	  if( rateWidth > rateHeight){
		  param.width =maxWidth;
		  param.height = height /rateWidth;
	  }else{
		  param.width = width /rateHeight;
		  param.height =maxHeight;
	  }
	}
	param.left = (maxWidth - param.width) / 2;
	param.top = (maxHeight - param.height) /2;
	return param;
}
*/
